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Variability in meta-analytic results concerning the value of cholesterol reduction in coronary heart disease: a
1Department of Family Practice, University of Texas Health Science Center, San Antonio 78284-7795, USA.
Insights
Cholesterol reduction
Area of Science:
- Cardiovascular Medicine
- Medical Statistics
Background:
- Conflicting results from meta-analyses on cholesterol reduction efficacy.
- Existing controversy surrounding the cardiovascular benefits of cholesterol lowering.
Purpose of the Study:
- To assess variability in meta-analyses on cholesterol reduction.
- To evaluate the cardiovascular value of cholesterol reduction and explain result discrepancies.
Main Methods:
- Systematic review of 23 meta-analyses published before 1995.
- Extraction of odds ratios for mortality and cardiovascular disease.
- Analysis of methodological, publication, and investigator variables.
Main Results:
- Heterogeneous results for total mortality, with limited support for cholesterol reduction.
- Homogeneous results for cardiovascular mortality and nonfatal cardiovascular disease, supporting cholesterol reduction.
- Methodologically stronger meta-analyses reported more favorable outcomes.
Conclusions:
- Variability in meta-analyses is influenced by inclusion criteria and investigator factors.
- Statistical significance of cardiovascular mortality odds ratios was key to perceived supportiveness.
- Evidence for cholesterol reduction's cardiovascular benefit is more consistent for cardiovascular outcomes than total mortality.
Abstract:
Despite official support for the efficacy of cholesterol reduction, considerable controversy exists, and meta-analyses of this topic have produced conflicting results. The authors assessed the variability of meta-analyses, evaluating the cardiovascular value of cholesterol reduction while attempting to explain the variability. Metaanalyses were identified by electronic search and citation tracking. Included were those conducted prior to 1995 that dealt with cholesterol reduction and total mortality, cardiovascular mortality, or nonfatal cardiovascular disease. In addition to extracting odds ratios for total mortality, cardiovascular mortality, and nonfatal cardiovascular disease, the authors encoded methodological variables, publication variables, and data concerning investigators' backgrounds. Twenty-three meta-analyses were reviewed, and 15 concluded that cholesterol reduction was beneficial. Summary odds ratios for total mortality were heterogeneous, generally failing to support the value of cholesterol reduction. Odds ratios depended on inclusion criteria and investigator variables. Odds ratios for cardiovascular mortality and for nonfatal cardiovascular disease were more homogeneous and supported the value of cholesterol reduction. Methodologically better meta-analyses tended to report more beneficial odds ratios. Although "supportiveness" of the value of cholesterol reduction was associated with inclusion/exclusion criteria and publication variables, the primary outcome variable related to supportiveness was the statistical significance of the odds ratios for cardiovascular mortality.